1. Field of the Invention
The present invention relates to a photodetector, in particular, to the photodetector with high power operation and large bandwidth in optical communication system.
2. Description of the Prior Art
As an information technology has been developed, an amount of information, which transmits through optical fibers, has been significantly increased. According to this trend, the photodetector requires a large bandwidth to receive a large amount of information and a high power operation.
When quantum wells are utilized in the photodetector, cladding layers having relatively small refractive index are stacked at both sides thereto for optical confinement. Thus, materials of large band gap are used for the cladding layer. InGaAsP material is generally used on a InP substrate in a device operable in wavelength band of 1.55 μm,.
However, energy band structure has a tendency of a discontinuity due to a difficulty of crystalline growth, and excited charges are subject to passing some barriers, so that it results in an increment of operating voltage and decrement of bandwidth.